Paper roll plug



United States Patent FOREIGN PATENTS 888,860 2/1962 Great Britain Primary Examiner Nathan L. Mintz AttorneySandoe, Hopgood & Calimafde ABSTRACT: This plug is for insertion into the end of a tubular core, on which rolls of paper or other sheet material are wound, to protect the core against damage when the roll is lifted or subjected to unsymmetrical pressure. The plug is constructed of material capable of withstanding the pressures to which the core is subjected particularly when being gripped by hoisting machinery, and is reinforced to distribute the loading when being inserted into a core and more especially when being withdrawn from a core. The plug surface has a coefficient of friction low enough to permit removal of the plug after use without breakage, and repeated use of the same plug, with resulting economy.

WIIIIIIIIIIIIIII I PAPER ROLL PLUG RELATED PATENT APPLICATION This application is a continuation-impart of our copending Pat. application Ser. No. 723,631, filed Apr. 23, 1968 for 5 Paper Roll Plug, now abandoned.

SUMMARY OF THE INVENTION 1 roll in a way which is not symmetrical around the circumference of the core, and this unsymmetrical loading often damages the core. If the core collapses and the paper reel gets out of round, so that a chuck cannot enter the core to hold the reel in an extruder, the entire reel of paper is unusable.

In order to protect the core, plugs are commonly inserted into the opposite ends of the core; but these plugs have been so difficult to remove that they are broken during removal after being used once or only a few times at most.

This invention provides an improved plug for bracing the ends of tubular cores. A short tapered portion at the inner end of the plug provides for convenient insertion, and the plug has a body portion of an outsidediameter to fit tightly within the core along sufficient axial length of the core to protectit against damage or collapse. No projection of the plug beyond the ends of the core is necessary; and the plug construction permits its insertion and removal without damage so that the same plug can be used repeatedly.

One feature of the invention is theconstruction of the plug from plastic material that provides a smooth surface for contact with the inside of a core of the size with which the plug is intended to be used, and which has a low enough coefficient of friction on the material of the core to be removable from the core without damaging the plug.

In the preferred construction there is a hub made from a metal pipe at the center of the plugfor receiving a tool by which the plug can be removed frorna core, and there are sturdy metal reinforcing rods extending from the metal pipe toward the periphery of the plug at angularly spaced locations around the hub for transmitting an extracting pull to the circumferential portion of the plug where friction resistance must be overcome.

The plug of this invention iscombined with the paperboard core, or other core, for holding reels of up to 7 tons of paper and for resisting the force of hydraulic clamps of hoisting r'nachinery that subjects the paper reel, at localized clamping areas, to pressures up to 3,000 lbs. per square inch.

The plug is preferably made of polyethylene which is available as waste material in some paper mills where polyethylene is used for coating paper. This material has ideal properties of compression and sheer strength, and low coefficient of friction for the purposes of this invention. When cast, the polyethylene locks around the metal frame of the plug.

The invention will be described as a core and plug assembly for a roll of sheet material since there is a correlation of the plug and the core which permits the removal of plugs from the ends of a core after use without damage to the plugs. The plug itself is claimed as a subcombination. Objects and features other than those already referred to will be described or become apparent as the specifications proceeds.

BRIEF DESCRIPTION OF THE DRAWING In the drawing, forming a part hereof, in which. like reference characters indicate corresponding parts in all the views:

FIG. 1 is an assembly view showing a tubular paper core with both ends reinforced by plugs embodying this invention;

FIG. 2 is a greatly enlarged, fragmentary view of one end of the roll shown in FIG. 1; and

FIG. 3 is a fragmentary end view of the plug and core shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a core 10, which is preferably made of heavy cardboard, and plugs 12 and 12' inserted in the opposite ends of the core. The plug 12 is shown in detail in FIG. 2 and it will be understood that the plug 12 is of similar construction.

At the center of the plug 12 there is a pipe 14 which constitutes the hub of the plug. This hub 14 extends for the full axial length of the plug 12 so that the end faces 16 of the pipe are flush with the end faces of the plug.

Reinforcing spokes 20 extend from the hub 14. Each of these spokes 20 is preferably a solid rod, though tubes can be used, if desired. The spokes are disposed in equiangular relation around the hub 14. Four spokes are shown in the illustrated construction, but more than four can be used on largesize plugs.

The spokes 20 preferably extend radially and each spoke is connected to the outside surface of the hub 14 by welding 24.

The remainder of the plug 12 is made of plastic 26, preferably cast polyethylene which locks around the metal frame formed by the hub 14 and spokes 20. This plastic forms a body portion 30 of the plug having a radius R which extends some distance beyond the ends of the spokes 20. The body portion 30 has an outer end face 32 which is plane and annular and preferably flush with the outer end'face of the pipe 14 which forms the hub of the plug.

At the inner end of the body portion 30, the plug l2has a tapered portion 40 which decreases in diameter as it 'extends inward toward an inner face 42 of the plug. This innerface 42 is parallel to the outer face 32 and is plane and annular and preferably flush with the inner face 16 of the pipe 14.

In the construction illustrated, the tapered portion 40 of the plug has an axial extent approximately equal to the axial extent of the body portion 30 which is of uniform diameter. The tapered portion 40 serves two purposes. It facilitates the entry of the plug into the end of the core 10,.and it also provides a mass of solid material homogenous with the body portion 30 for providing additional strength against compression without increasing the area of contact of the plug with the inside surface of the core. This makes-possible easier removal of the plug from the core after the core has been used and the plugs are to be reclaimed.

The body portion 30 of the plug 12 has an outside diameter substantially equal to the inside diameter of the core 10 so that the plug 12 fits within the core tightly and with substantially a press fit." No particular problem is involved in pressing the plug into the core because the entire surface 32 is exposed and pressure can be distributed over this surface to force the plug into the core without danger of breaking the plug.

The application of force to the plug to remove it from the core presents a problem and a hook or other tool inserted through the pipe 14 does not apply force evenly over the area of the inner face 42. The tool pulling the plug from the core is likely to concentrate the pull against the inner end face 16 of the pipe 14 and this force is distributed throughout the plug 12 by the spokes 20. The polyethylene, or other plastic, of which the plug 12 is made, is not brittle and haselastic properties which permit internal stress to be distributed throughout the plastic by the spokes 20. It is a feature of the preferred embodiment of the invention that the spokes 20 are located in the body portion 30 and that they extend most of the way from the hub 14 to the outer circumference of the plug where the friction of the plug against the inside surface of the core must be overcome.

If the plug 12 is removed from the core 10 by striking the inner face 42 at its center region, the shocks are absorbed by the polyethylene without cracking and the force of the blows is transmitted through the metal of the pipe 14 and through the spokes 20 to the outer portions of the plug to overcome its friction against the core, as previously explained.

It is another feature of the invention that the plug 12 is made of material having a smooth surface which does not lock into the inside surface of the core. The coefficient of friction of the circumference of the plug on the inside surface of the core is low enough to permit the surface of the plug and core to slide on one another without damage to the plug surface. in the preferred combination of this invention, this coefficient of friction is that of smooth, cast polyethylene on heavy cardboard. The use of wooden plugs for the purposes of this invention has been quite unsatisfactory in practice. it is extremely difficult to remove the plugs without damaging the wood. It will be understood that plugs reused for the purpose of this invention must maintain their circumference accurately not only to insure a tight fit in the core but also to insure an accurately round core when reinforced by driving in a plug.

In the preferred construction, the inside diameter of the hub 14 is preferably approximately percent to 15 percent of the diameter of the plug and the axial length of the plug is approximately percent to percent of its diameter. The spokes 20 are conveniently made of concrete reinforcing rods having a diameter of approximately three-eighths inch welded to a pipe 14 of one-eighth inch wall thickness. It is sufficient for the spokes 20 to terminate at a distance from the plug circumference equal to approximately one-sixteenth of the plug diameter or less than twice the diameter of the ends of the spokes that are near the circumference of the plug. The spokes can extend closer to the circumference. These values are given by way of illustration.

The body portion of the plug has an axial length equal to at least the length of the tapered portion of the plug, and the axial length is between 5 percent and percent of the plug diameter.

Although this invention is intended primarily for reinforcing heavy paperboard tubular cores, it can be used with other kinds of cores. if the core is made of a plastic material, or any material, it is important to avoid combining a plug material and a core material which will freeze to one another when allowed to stand in contact under high pressure for considerable periods of time. The coefficient of friction of the plug 12 on the surface of the core 10 should be a coefficient which remains reasonably constant over the periods of intended use ofthis invention.

The preferred embodiment of this invention has been illustrated and described, and the invention is defined in the appended claim.

We claim:

1. A plug for reinforcing the ends of a tubular core on which is wound a roll of paper or the like, said plug comprising a cylindrical body portion having an outside diameter that fits tightly into the end of a core with which the plug is intended to be used, a tapered portion ahead of the body portion for facilitating entry of the plug into the core, a hub at the center region of the plug, the hub being tubular and coaxial with the plug so as to provide a center opening through the plug, and a frame reinforcing the plug and including spokes connected with the hub and extending radially upward therefrom for most of the distance from the hub to the circumference of the plug that contacts with an inside surface of the core.

2. The plug described in claim 1 characterized by the body portion and the tapered portion of the plug being made of the same kind of plastic material, and said material enclosing the reinforcing spokes.

3. The plug described in claim 1 characterized by the hub being a section of metal pipe and the spokes being radial metal rods rigidly secured to the hub.

4. The plug described in claim 3 characterized by the spokes being welded to the metal pipe so that the pipe and spokes form a one-piece metal frame within the plug.

5. The plug described in claim 4 characterized by the plug other than the frame comprising a plastic mass having parallel inner and outer faces flush with the end faces of the pipe that forms the hub of the plug.

6. The plug described in claim 1 characterized by the body portion and the tapered portion of the plug being a one piece mass of polyethylene that encloses and locks around the spokes of the reinforcing frame.

7. The plug described in claim 1 characterized by the combination with the plug of a tubular core in one end of which the plug is inserted with the tapered end of the plug innermost core without damage to the plug.

8. The combination described in claim 7 characterized by all of the spokes being positioned axially in the plug so as to be located in the body portion of the plug that contacts with the inside surface of the core for transmitting axial force from the center hub through the spokes to the region of the plug which is in contact with the inside surface of the core, said spokes terminating short of the circumference of the plug by a distance less than twice the diameter of the ends of the spokes that are near the circumference of the plug.

9. The combination described in claim 7 characterized by the plug being inserted fully into the end of the core and the outer face of the plug being flush with the end of the core, the core being made of heavy paper board. I

10 The combination described in claim 7 characterized by the inside diameter of the hub being approximately 10-15 percent of the diameter of the plug and the axial length of the plug being approximately 20-30 percent of its diameter, the spokes being rods having a diameter approximately three times the thickness of the pipe which forms the hub, and the distance from the termination of the spokes to the circumferential surface of the plug being approximately one-sixteenth of the plug diameter.

11. The combination of two reinforcing plugs of annular cross section, a tubular core with one of the plugs inserted into each end thereof, each plug being made of polyethylene and having a tapered forward end portion for facilitating entry of the plug into the core, the tapered portion being out of contact with the core when the plug is in working relation with the core, and the plug having a body portion that fits into the core with a press fit and that has a circumferential surface that is smooth and free of projections whereby it is held in the core by friction without distorting any part of the core surface outward, the plug having a center opening for receiving an axle on which the plugs, core and a reel on the core rotate, the center opening being longer than the circumferential friction surface of the plug, a metal pipe lining said opening and constituting a hub of the plug, said plug having an annular face at the inner end of the center opening for contact with a tool that pulls the plug out of an empty core for subsequent use in another core, and means for strengthening the plug against distortion by force transmitted from the annular face around the inside of the axle opening and through the plug to the circumferential surface of the plug in friction contact with the core including material of the core having an axial cross section of substantially the same axial length as the center opening around substantially the full angular extent of the plug and all the way to the circumference of the plug, the friction surface of the plug holding the plug in the core during shipping of a sheet material reel wrapped on the core and to protect the core from distortion and collapse when the reel is picked up by grippers of hoisting machinery which apply unsymmetrical loading to the circumference of the reel, the radial plane strength of the plug being correlated with the coefficient of friction of the smooth cylindrical surface of the circumference of the plug on the inside surface of the core to permit the plug to be pulled out of the tubular core without damage when subjected to an extracting force applied axially against said annular face of the plug by a tool inserted through the axle opening of the plug.

12. The combination described in claim 11 characterized by the body portion of the plug having an axial length equal to between 5 percent and 35 percent, of the diameter of the plug, most of said axial length being that of said circumferential surface that is in frictional contact with the inside surface of the core, and said means for strengthening the plug including a pipe lining the axle opening, the pipe being secured to the rest of the plug for preventing axial movement of the pipe with respect to the material of the plug surrounding the pipe. 

